The present invention relates to the monitoring of processes, particularly in installations where a large number of processes which are identical with respect to at least one process parameter are being performed.
In many installations of this type, it is frequently necessary to monitor all of the ongoing processes, and the monitoring results are employed to derive diagnoses of the condition, or status, of each individual process. It may be desired, for example, to monitor at least one operating parameter of each process and to test or compare various measured parameters according to specified rules in order to arrive at diagnoses indicating the operating state of each process, and thus of the component or components controlling the process. These operations may be carried out in a digital computer in which each rule is constituted by a programming subroutine.
Such a procedure is employed in diagnostic expert systems in which selected items of information relating to the processes are compared or combined according to specified rules in order to produce diagnostic information. In certain systems, there are a large number of essentially identical processes which are being performed simultaneously and which all have the same nominal operating parameters or at least one nominal operating parameter in common. For example, a boiler may contain a waterwall composed of a large number of tubes through which water is flowing while being heated. These tubes are nominally identical in that they are all associated with the same flow and heat distribution conditions. The conditions in each tube may be monitored by a temperature sensor, as well as other components, and the output readings of each temperature sensor must be examined as part of an overall monitoring and diagnostic system.
It is known to monitor the readings produced by a variety of condition sensors and to test and combine the monitoring results according to various rules developed on the basis of recommendations provided by individuals possessing expertise in the operation of the apparatus being monitored. Therefore, these monitoring and diagnosis systems are known as expert systems. One exemplary system of this type is disclosed in U.S. Pat. No. 4,644,479, which issued on Feb. 17, 1987 to Kemper et al.
Known expert systems interpret sensor readings and combine the interpreted readings from various sensors to produce diagnoses of the operating conditions of components and subsystems of the apparatus being monitored. These operations are carried out according to various rules which provide indications, inter alia, of the validity of the sensor readings or the level of confidence in the sensor readings, measures of belief and disbelief in the resulting diagnosis, the severity, importance and priority of malfunction diagnosis, etc.
When the apparatus or plant being monitored has a large number of nominally identical components in which nominally identical processes are being performed, a set of instructions must be provided for implementing each rule associated with each sensor output evaluation and each diagnostic step. Each set of instructions is generally provided in the form of a subroutine stored in memory. Since it has heretofore been the practice to provide a separate set of instructions for each rule which is to be applied to the output of each sensor, a considerable amount of programming time must be employed and a considerable amount of memory capacity must be provided when a large number of identical processes are to be monitored.
Heretofore, attempts have been made to reduce the amount of programming time required for implementing a given rule by creating an appropriate subroutine containing the instructions applicable to each sensor, this being called a template, and then duplicating that subroutine for each nominally identical sensor. While this procedure introduces some simplification to the programming effort, it nevertheless requires a considerable memory capacity for storage for all copies of each subroutine.